Phase 3C: Deployment pipeline & Store-and-Forward engine

Deployment Manager (WP-1–8, WP-16):
- DeploymentService: full pipeline (flatten→validate→send→track→audit)
- OperationLockManager: per-instance concurrency control
- StateTransitionValidator: Enabled/Disabled/NotDeployed transition matrix
- ArtifactDeploymentService: broadcast to all sites with per-site results
- Deployment identity (GUID + revision hash), idempotency, staleness detection
- Instance lifecycle commands (disable/enable/delete) with deduplication

Store-and-Forward (WP-9–15):
- StoreAndForwardStorage: SQLite persistence, 3 categories, no max buffer
- StoreAndForwardService: fixed-interval retry, transient-only buffering, parking
- ReplicationService: async best-effort to standby (fire-and-forget)
- Parked message management (query/retry/discard from central)
- Messages survive instance deletion, S&F drains on disable

620 tests pass (+79 new), zero warnings.

src/ScadaLink.ConfigurationDatabase/Configurations/DeploymentConfiguration.cs

@@ -41,6 +41,33 @@ public class DeploymentRecordConfiguration : IEntityTypeConfiguration<Deployment
     }
 }
 
+public class DeployedConfigSnapshotConfiguration : IEntityTypeConfiguration<DeployedConfigSnapshot>
+{
+    public void Configure(EntityTypeBuilder<DeployedConfigSnapshot> builder)
+    {
+        builder.HasKey(s => s.Id);
+
+        builder.Property(s => s.DeploymentId)
+            .IsRequired()
+            .HasMaxLength(100);
+
+        builder.Property(s => s.RevisionHash)
+            .IsRequired()
+            .HasMaxLength(100);
+
+        builder.Property(s => s.ConfigurationJson)
+            .IsRequired();
+
+        builder.HasOne<Instance>()
+            .WithMany()
+            .HasForeignKey(s => s.InstanceId)
+            .OnDelete(DeleteBehavior.Cascade);
+
+        builder.HasIndex(s => s.InstanceId).IsUnique();
+        builder.HasIndex(s => s.DeploymentId);
+    }
+}
+
 public class SystemArtifactDeploymentRecordConfiguration : IEntityTypeConfiguration<SystemArtifactDeploymentRecord>
 {
     public void Configure(EntityTypeBuilder<SystemArtifactDeploymentRecord> builder)